More particularly, the invention relates to a folded tube comprising a metal strip folded on itself so as to delimit two parallel channels separated by a spacer, which, results from the joining of two borders of the strip each folded at right angles towards the inside of the tube from an outer face of the tube, forming a folded outer edge.
Folded tubes of this type are already known, and exhibit a cross-section of flattened shape and possess two flat and parallel large faces, joined together by two small curved faces. Such tubes serve to form a bank of tubes obtained by an alternate stacking of tubes arranged in parallel and of corrugated spacers, forming heat-exchange fins, which extend between the large faces of the tubes.
The ends of the tubes are accommodated with holes of appropriate shape formed by manifold plates which are capped by manifold chambers. The assembly is brazed in an appropriate furnace so as to constitute a heat exchanger.
In the majority of the known tubes of this type, the folded outer edge exhibits a circular-arc shape which results from the folding operation, so that a depression is always created at the surface of the tube at the place where the border is folded inwards. It is therefore necessary to fill in this depression, to ensure continuity of each of the large faces or the tubes in the regions close to the spacer and to ensure leaktightness of the joint between the tubes and the manifold plates of the heat exchanger. Such operation raises a practical difficulty, since it is difficult to fill in this depression conveniently with brazing alloy during the manufacture of the tube.
Tubes of this type are also known in which the folded outer edge exhibits a sharp outer corner, which eliminates the depression mentioned above. However, the shaping of a sharp-cornered outer edge poses practical implementation difficulties
Moreover, the known tubes of the abovementioned type all have the drawback of not allowing the corrugated spacers to be held properly, which generally makes it necessary to have special tooling to keep these spacers in the correct position during the brazing of the heat exchanger.